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NATURAL SELECTION 
vi 
nests of many of the swifts and swallows, as well as that of 
the song-thrush — peculiarities of habits which ultimately 
depend on structure, and which often determine the material 
most frequently met with or most easily to be obtained. 
Modifications in any of these characters would necessarily 
lead either to a change in the materials of the nest, or in the 
mode of combining them in the finished structure, or in the 
form or position of that structure. 
During all these changes, however, certain specialities of 
nest-building would continue for a shorter or a longer time 
after the causes which had necessitated them had passed 
away. Such records of a vanished past meet us everywhere, 
even in man’s works, notwithstanding his boasted reason. 
Not only are the main features of Greek architecture mere 
reproductions in stone of what were originally parts of a 
wooden building, but our modern copyists of Gothic archi- 
tecture often build solid buttresses capped with weighty 
pinnacles to support a wooden roof which has no outward 
thrust to render them necessary ; and even think they 
ornament their buildings by adding sham spouts of carved 
stone, while modern waterpipes, stuck on without any attempt 
at harmony, do the real duty. So, when railways superseded 
coaches, it was thought necessary to build the first-class 
carriages to imitate a number of coach-bodies joined together; 
and the arm-loops for each passenger to hold on by, which 
were useful when bad roads made every journey a succession 
of jolts and lurches, were continued on our smooth macadam- 
ised mail-routes, and, still more absurdly, remain to this day 1 
in our railway carriages, the relic of a kind of locomotion we 
can now hardly realise. Another good example is to be seen 
in our boots. When elastic sides came into fashion we had 
been so long used to fasten them with buttons or laces, that 
a boot without either looked bare and unfinished, and accord- 
ingly the makers often put on a row of useless buttons or 
imitation laces, because habit rendered the appearance of 
them necessary to us. It is universally admitted that the 
habits of children and of savages give us the best clue to the 
habits and mode of thought of animals ; and every one must 
have observed how children at first imitate the actions of 
1 Since this was written they have generally been disused. 
